Effect of Dietary Retinyl Acetate, β-Carotene and Retinoic Acid on Wound Healing in Rats

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Abstract
The effects of feeding various levels and combinations of retinyl acetate, β-carotene, or retinoic acid on skin wound healing in rats was investigated. Weanling male Sprague-Dawley rats were fed a vitamin A-free diet for 2 weeks to produce marginal vitamin A status. After a paravertebral incision was made and closed with suture, one of several diets were fed for either 5 or 14 days. Surgery and recovery did not reduce liver vitamin A nor serum retinol levels compared to nonoperated pair-fed controls. Supplemental retinyl acetate feeding at five times the NRC-suggested allowance resulted in a mild, but significantly increased postmortem wound tensile strength after 5 days compared to rats fed the suggested allowance. Although a low level of retinoic acid in the diet (1.3 µg/g diet) depressed wound strength at 5 days, a higher level (5.2 µg/g) increased the strength 57% above controls. Still higher levels (49.1 µg/g) did not further increase the tensile strength of the wound. β-Carotene fed at the requirement level for 5 days (with compensation made for utilization as one-sixth that of retinol) doubled wound strength compared to rats fed the requirement as retinyl acetate. Vitamin A feeding did not enhance wound strength after 14 days of feeding. It is concluded that supplemental retinyl acetate, β-carotene, or in some cases all-trans-retinoic acid can be effective in enhancing wound strength, 5 days but not 14 days after surgery, of young male rats with marginal vitamin A status.